Footwear



Nov. 17,1942.v p, R, AUST, 2,302,161

FOOTWEAR Filed June 14, 1940 "-5 -Q J6 *JAN /Zzer ,fila 7 9 (2|Polyamide ,1'1" l w 5 I9V I5 /medr'la/ Y UZ. 'e

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Patented Nov. 17, 1942 UNITED sTATEs PATENT OFFICE Y FOOTWEAR Paul R.Austin, Wilmington, Del., assignor to E. I. du Pont de Nemours &Company, Wilmington, Del., a corporation of Delaware Application June14, 1940, Serial No. 340,594

3 Claims. ('Cl. 12-142) This invention relates to articles of footwear,and more particularly to the manufacture of such articles from syntheticmaterials.

Heretofore it has been almost universal practice to fabricate footwearfrom leather, i. e., fromtanned animal hides or skins. However, shoesmade of leather have certain serious drawbacks.

. Depending somewhat on the kind of leather used,

they are subject to scufing, the familiar unsightly marring whichresults when the shoe ac- Acidentally is brushed against a roughsurface.

Furthermore, the repeated flexing to which shoes are subjected inwalking results in permanent sharp creasing of the leather into wrinklesresembling crows feet, which damage the appearance of the shoe. Mostfootwear must also be refinished frequently by waxing and polishing.Leather shoes are expensive, due to a number of factors: The conversionof hide into leather requires a considerable number of processing steps,which add greatly to its cost. A large proportion of the hides used areimported, which increases cost and makes the supply uncertain.

' There is considerable waste in cutting leather into shoe parts,because of the presence of brand marks, briar scratches, scars producedby parasite infestation, and the like. Leather is nonuniform, varyinggreatly in thickness, strength and resilience from one point to anotheron the same hide, so that great care is required in cutting leather forshoes which results in relatively high labor costs,

Materials other than leather have found some application in certainparts of shoes such as soles, heels, linings, and innersoles. However,success in the use of synthetic materials in the uppers of shoes andslippers has hitherto been small.

groups as an integral part of the main chain of atoms in the polymers.These polymers will be referred to herein as polyamides. By highmolecular weight polyamides are meant those which have been polymerizedto a sufllciently high degree to be capable of formation into toughfilaments and films. The `polyamides do not -in general exhibit theseproperties unless they have an intrinsic viscosity yof at least 0.4,where intrinsic viscosity is defined as in Patent 2,130,948.

The high molecular weight polyamides used in the practice of thisinvention are of the ygeneral types described in Patents 2,071,250,2,071,253 and 2,130,948. For the most part they are crystalline ratherthan resinous, their microcrystalline nature being evidenced by the typevof diffraction pattern 'which they' furnish `on X-rayexamination. Sinceone of the most characteristic properties of these polyamides is theirability to be formed into pliable fibers, they are referred to asfiber-forming polyamides" or isuperpolyamides. Filaments spun from thesepolyamides, e. g. by extrusion of the molten polymer, yield, upon colddrawing, fibers which show by characteristic X-ray diffraction patternsorientation along the fiber axis.

The polyamides are obtainable from bifunctional polyamide-formingreactants, as for instance from the reaction of diamines and dibasiccarboxylic acids, the self-polymerization ofA boxylic acid andmonoaminomonocarboxylic acid The uppers of shoes are subjected toconstantly I repeated flexing and stretching. The synthetic materialshitherto available have not been sumciently tough to withstandsatisfactorily these conditions, and have failed by cracking andsplitting.

This invention has as an object new articles of footwear which have goodwearing properties and which retain their initial appearance over longperiods of service. A further object is the manufacture of a low costfootwear characterized by freedom from cracking, scufling and wrinkling.Other objects will appear hereinafter.

These objects are accomplished by fabricating articles of footwear'andparticularly the -uppers of shoes, slippers and the like, from materialscomprising high molecular Weight synthetic linincludes alsoamide-forming deriva ives thereof. Upon hydrolysis with mineral acids,the polyamides yield monomeric bifunctional amideforming reactants. Forexample, a polyamide 40 derived from a diamine and a dibasic carboxylicacid, on hydrolysis with hydrochloric acid, yields the dibasiccarboxylic acid and diamine hydrochloride. Similarly a polyamide of theamino acid type yields an amino acid hydrochloride on hydrolysis withhydrochloric acid. The polyamides'most useful in this invention arethose having intrinsic Vviscosities betweenv 0.5 and 2.0 and meltingpoints between 90 and 300 C. In the accompanying drawing:

Fig. 1 is a side view of a shoe embodying my invention,

Fig. 2 is a section through the line A-A in Fig. 1, and

Fig. 3 is an elevation of the -heel end of the ear polymers containingamide or thioamide shoe shown in Fig. 1.

'I'he invention is illustrated in its preferred form in the drawings inwhich the shoe upper, indicated generally by the character A, iscomposed of a flexible fabric coated with synthetic linear polyamide.This coating, exaggerated in thickness for illustration, is indicated bythe numeral 20, That section of the upper designated as l is known asthe toe cap, 2 is known as the vamp, while 3 is known as the quarter.Further exposed portions of the article of footwear represented in Fig.1 include 4, the heel covering; 5, the heel; 6, the heel lift; and I0,the outsole. In Fig. 2 the tongue is designated by 22, and the laces by2 I. The vamp lining is shown by l, and the sole construction includesl0, the outsole; Il, the filler; I2, the insole; and I3, the socklining. In the particular structural embodiment of the invention shownin Fig. 2, the sole portions of the article of footwear are combined andattached to the upper by McKay stitching. Lasting tacks are indicated byi6, and clinched at l1. The stitching i5 is applied through the channelI4, in the outsole I0, and extends through to the insole l2. Structuraland lining portions of the upperv l, 2, 3, are shown in Fig. 1 where 8is a box toe or toe stiifener, while the heel section is stiffened b y acounter designated by 9. The position of the counter with respect toother underlying portions of the quarter 3, is shown in Fig. 3 where thequarter lining I9 protects the foot from the counter 9 which in turn isseparated from the quarter section of Ithe upper 3 by a lining I8.

In the preferred-and most valuable practice of my invention the shoeupper consists of a flexible fabric coated with a high molecular weightinterpolyamide. The interpolyamides are formed by the conjointpolymerization of a mixture of polyamide-forming reactants capable ofyielding more than one polyamide if reacted in suitable combinations. Atypical example is the interpolyamide derived from a dibasic acid, adiamine, and another dibasic acid and/0r another diamine, sucn as theinterpolyamide derived from adipic acid, hexamethylenediamine, sebacicacid and decamethylenediamine. A particularly useful class ofinterpolyamides are those derived from a dibasic acid, a diamine and anamino acid or amide-forming derivative thereof, such as theinterpolyamide derived from adipic acid, hexamethylenediamine andcaprolactam or from adipic acid, hexamethylenediamine and12-aminostearic acid.

The polyamide coated fabric forming the upper y of the shoe may beobtained by several methods, as for instance, by deposition of thepolyamide on the fabric from solution or dispersion, by coating orimpregnating a suitable fabric with the molten polymer, by calenderingor vby pressing with heat and pressure a preformed sheet of the polymeron the fabric. A preformed sheet of the polymer can also be applied tothe fabric by means of an adhesive, this method being preferred when thesheet has been cold rolled.

A further methodof practicing the invention consists in using as thematerial for the shoe upper a self-supporting sheet of the polyamidefilm in suitable thickness. These sheets may be extruded through a slitfrom the molten polymer and tempered by quenching or otherwise rapidlychilling. Sheets of the desired thickness may also be obtained fromsolutions or by slicing them from a block of the molded polyamide. Thesesheets, in order to impart the tensile strength and other propertiesdesired in shoe uppers are preferably cold worked, usually by coldrolling, which consists in applying compressive stress to the solidpolymer thereby orienting the crystallites along one or more preferredaxes, and are embossed at elevated temperature. In this process theamount of cold rolling should be at least to the extent of 10%elongation.

The following examples, in which parts are by weight, illustrate theinvention in greater detail.

Example I Two hundred parts of an interpolyamide having an intrinsicviscosity of 0.92 derived from 60 parts hexamethylenediammonium adipateand 40 parts caprolactam is dissolved, along with 200 parts ofamylbenzenesulfonamide as plasticizer, in 400 parts of a mixture ofethanol and water in the ratio 16:5. Two coatings of the solution areapplied to a section of 1.32-53" unsized sateen by spreading thesolution on the fabric with a leveling blade and drying the coatedfabric in a heated chamber with circulation of air at 65 C. after eachapplication. The resulting coating is termed a sub-coating.

A color coat solution" is then prepared consisting of 870 parts of theinterpolyamide described above, 356 parts of amylbenzenesulfonamide, 214parts of butyl phthalyl butyl glycolate, and 16 parts of carbon black-in2602 parts of a mixture of ethanol and water in the ratio of 16:5. Asuilicient number of coatings of this color solution is then applied tothe sub-coating to build up on the fabric a coating 0.007" thick. Theresulting coated fabric is subjected to embossing with a leather grainat 82 C. The upper stock thus obtained is employed in the fabrication ofa pair of womens Oxfords of McKay construction. These Oxfords providefoot comfort, re-

tain their original shape and, after extended se. vice, are found to befree from scuiing and cracking. A further sample of the coated fabricjust described is employed in the fabrication of a pair of womensOxfords of cemented construction. These shoes are found to be equallydurable and after extended wear show no tendency for separation of thesole.

A high gloss finish of patent leather type, in appearance is obtained onthe above described upper stock by applying two coatings of solution ofl0 parts of the above described interpolyamide in 90 parts of a solventconsisting of trichloroethylene and methanol in the ratio 15:16. Theresulting material is employed in the fabrication of a pair of womensOxfords of McKay construction, which after extended usage are found toretain their original glossy finish to a high degree.

Example II A sub-coating solution is prepared consisting of 4 parts ofthe interpolyamide of intrinsic viscosity 0.92 derived from 60 parts ofhexamethylenediammonium adipate and 40 parts of caprolactam, 4 parts ofamylbenzenesulfonamide, 6.4 parts of ethanol, and 1.6 parts of water.The solution is applied in two coats to a section of 7.00-40" blackcotton sheeting using conventional fabric coating equipment whichprovides for drying between coats at C. In the preparation of the colorcoating solution" 5 parts of bone black is mixed with 12 parts of theinterpolyamide of intrinsic viscosity 1.05 derived from 60 parts ofhexamethylenediammonium adipate and 40 parts of -aminocapronitrile, 5.81parts of amylbenzenesulfonamide, 3.25 parts of butyl phthaiyl butylglycolate, 27.32 parts of ethanol,

and 6.88 parts of water. This mixture is heated and stirred until thepolyamide is found to be in solution, and then cooled to roomtemperature for use in coatings. Coatings of this solution are appliedto the sub-coated sheeting until the total weight of solvent-freecoating on vthe fabric corresponds to 7.6 oz./40 yard. The resultingcoated sheeting is then backed with a rubber impregnated sheeting usingstandard textile combining machinery and the product given a leathergrain by embossing at 80 C. The adhesive used to yield the doubletextured product is rubber cement.

The double textured upper stock described above is employed in thefabrication of a pair of childs sport welt shoes having rubber soles anda Goodyear welt construction. This type of footwear, designed for hardusage, is found to be of attractive appearance and outstandingdurability.

Example III Erample IV,V

Polyamide sheets ranging in thickness from 0.015 to 0.030 prepared froma composition containing 1600 parts of an interpolyamide of intrinsicviscosity 0.86 derived from equal parts of hexamethylenediammoniumadipate and decamethylenediammonium sebacate, 685 parts of a mixture ofN-ethyl ortho andparatoluene sulfonamides and 16 parts of carbon blackare cold rolled by passing them through chromium faced ,rolls undersuilicient pressure to cause elongations of 50-140%. The sheets are coldrolled in two directions which are at right angles to each other. Thecold rolled sheeting obtained in this way is embossed in a plate presswith a pin seal pattern at a tempera/ture of 85-88" C.

The resultmg sheetmg possfgses a leather-:mmf ,4. The closely wovenfabric base to which the polyfeel, combined with high si; ngth andexcellent drape.

A samplev of the polyami'ciensheetingis then employemas upper materialin the fabrication' of a pair of'chiids ballet slippers.: Standard shoefabrication equipment vand processes are employed-.throughout as theupper stock is cut into the component parts lof the up r using the usualdiesand backed with a light Aeece lining using a vstandard latexadhesive. Tlfe various parts of I the upper are thei assembled aiid sewntogether #to smooth seams Without buckling 4vpr distortion.

'I'he uppers are attached to a composition innersole by thefcustomaryprocedures o'f first pulling over, and side, toe and heel lasting. Aleather outsole is then attached byvstitching on a McKay machine. Afterattaching the heel, inserting sock lining and completing surface vfinishing operations. the finished pair of childs ballet slippers arefound to be well shaped and to have an exceedingly attractiveappearance.

A pair of womans Oxfords are similarly fabricated using the same uppermaterial and the shoes obtained are found to be highly resistant toscuiing and surface marring during wear.

In anfanalogous manner white shoes are fabricated from upper materialconsisting of a cold rolled upper stock containing 65% of theinterpolyamide derived from equal parts of hexamethylenediammoniumadipate and decamethylenediammonium sebacate having an intrinsicviscosity of 0.86, 25% of a mixture of N-ethyl ortho and paratoluenesulfonamide, and 10% of titanium dioxide pigment.

Example V To the square side of a section of 1.32-53 unsized high count(108 x 96) sateen are applied two coats, with drying at 88 C. betweencoats, of a sub-coating solution consisting of 39 parts of aninterpolyamide. (melt viscosity 3148 poises at 250 C.) derived from 40parts ofv hexamethylenediammonium adipate, 30 parts ofhexamethylenediammonium sebacate, and 30 parts of 6- aminocaproic acid;15.6 parts of the product obtained by condensing phenol withyL12-octadecanediol in the presence of zinc-chloride; 10.4 parts of theproduct prepared by ester interchange of propyleneglycol with castorroilin the presence of potassium hydroxide; 80 parts of ethanol; and 17.5parts of water. Eleven coats of a color coat solution consisting of 6parts of carbon black dispersed in 700 parts of solution having the samecomposition as the sub-coating solution are then applied at about C. tothe previously coated surface, with drying at 88 C. between coats. Afterthe application of the sixth color coat, the product is skivered byembossing with a line kid grain at 93 C. The total weight of thecoatings applied is 9.8 oz./50 yd. The final product is again embossedat 93 C. with a. fine kid pattern. The upper stock thus obtained isemployed in the fabrication of womens sport-type pumps to which outsolesare attached by a pyroxylin cement. Womens sport-type pumps containingthe same upper material are also made to which outsoles are attachedwith the use of` a plasticized interpolyamide cement. 'Ihese shoes areextremely well shaped to the last, and the soles are found to be rmlyattached. The high quality of the upper surface in terms of initialappearance and freedom during wear from all damage such as cracking orscumng is particularly outstanding.

vfabrication steps.

One of the most valuable embodiments of my invention is a shoe in whichthe upper consists of a. polyamide coated knit fabric. A shoe of thiskind is described in the following example.

Example VI A sub coat solution is prepared consisting of 128 parts ofthe interpolyamide derived from 60 parts of hexamethyldiammonium adipateand 40 parts of epsilon-caprolactam having a melt viscosity of 4585poises at 250 C.; 95 parts of 1,12- diphenyloloctadecane; 32 parts ofthe condensation product of propylene glycol and castor oil; 192 partsof ethanol; and 64 parts of water. The mixture is heated and stirreduntil a clear solution is obtained. The hot solution is applied in 2coats by means of a doctor `knife to a double textured fabric comprising2 layers of cotton knit fabric weighing '71A oz./sq. yd. cementedtogether by means of a nonvulcanizing rubber cement, drying betweencoats in a heated chamber with circulation of air at 65 C. The colorcoating solution consists of 686 parts of the interpolyamide describedabove; 536.8 parts of L12-diphenyloloctadecane; `152.4 parts of thecondensation product of propylene glycol and castor oil; 24.8 parts ofcarbon black; 1575 parts of ethanol; and 525 parts of water, heated andstirred until homogeneous. Coatings of this solution are applied to thesub-coated composite fabric until the total weight of solvent-freecoating on the fabriccorresponds to 10.1 oz./50" yd.

After the application of a leather grain by embossing at 9399 C., theresulting upper stock is employed in the fabrication of a pair of womensclosed Oxfords of McKay construction. These shoes are found to beaccurately shaped to the last, and of a most attractive appearance.

A shoe the upper of which is composed of polyamide coated textilefabric, such as cotton, is a particularly desirable embodiment of thisinvention since this material exhibits especially desirable workingproperties in the lasting and other fabrication steps involved in themanufacture of footwear. In some instances the use of the polyamides inother forms may be desirable, as for instance in the form ofself-supporting sheets as previously mentioned or in the form of spongypolyamides consisting of multicellular sheet containing fine voids orpores and obtained by melting under pressure finely divided polyamide inan inert gas and extruding the molten polyamide containing the entrappedgas bubbles into lm and quenching. These porous films, which will ingeneral have apparent densities less than 0.8, are best used whencombined with a flexible backing such as cloth by means of a suitableadhesive. A coating having a high degree of porosity may also beobtained by subjecting a coating containing a substantial amount ofsolvent to heat and pressure. A further method of preparing a porouspolyamide coated fabric consists of introducing semi-microscopic holesinto the coated fabric by perforation techniques.

Upper material prepared by the described methods is generally given adecorative surface to resemble leather. Various leather grains arereadily impressed upon the surface of the upper material by embossingprocedures. Effective embossing is readily secured at temperaturessubstantially below the melting point of the polyamide film or coatedflexible material under consideration.

A further type of upper material comprising polyamides, useful inpreparing the products of this invention consists of a textile fabricsuch as may be prepared by weaving or knitting polyamide fibers. A stillfurther type of upper material may be prepared by felting together shortber lengths of a suitable polyamide.

The polyamide composition may contain selected modifying agents, such asplasticizers, pigments, dyes, antioxidants, and the like. The preferredcomposition contains polyamide and plasticizer in ratios varying from90:10 to 50:50. Particularly useful plasticizers are high boilingarylsulfonamides and phenols or mixtures thereof. A wide variety ofcommon dyes may be used to manufacture the polyamide upper material in alarge variety of shades.

In the preferred practice of building up a coating on a fabric base byapplication thereto of a polyamide solution, the coating should have athickness between 0.001" and 0.030", and preferably between 0.002" and0.010". Preformed sheets may be bonded to the fabric base by heat andpressures, or after cold rolling these sheets may be combined to thefabric with an adhesive which desirably consists of a solution of thepolyamide. The entire upper of shoes can be made of the polyamide coatedfabric, or if desired, only a part of the upper, e. g. the vamp.

Selection of the textile base depends largely on the working propertiesand strength desired in the final polyamide coated fabric. Among usefulsingle textured backing fabrics may be mentioned sateens, twills,sheetings, elastic Woven fabrics and the like. Nonraveling backings, asrepresented by rubber impregnated fabrics are especially useful.Multiple textured fabrics are frequently desirable. For example, anupper stock constituted of a polyamide coating on a high count sheetingto which in turn is cemented a loosely woven nonraveling fabric, yieldsan upper stock which is free of any tendency for clothy appearance onstretching, is strong yet flexible, and provides for a nonraveling edge.Unwoven lfabrics, e. g. felts, can also be used as backings or supportsfor the polyamide coatings.

The manufacture of improved shoes by fabrication from the fiber-formingsynthetic linear polyamides of shoe parts other than the uppers is alsowithin the scope of this invention. The heel covering shown in thedrawing at 4 and tongue 20 may be prepared of much the same type ofmaterial as is employed in the upper. Similarly, lining materials suchas 1 and i8 may comprise polyamide, for example, in the form of atextile fabric. Coated fabrics, in whichthe coating comprisespolyamides, are advantageous- Yly used in the sock lining I3 and thequarter lining I9. Toe and heel stiffeners such as the box toe 8 and thecounter 9 may be prepared in a number of ways employing polyamide, amongwhich may be mentioned the impregnation of coarsely woven textilefabrics with a soluble polyamide or with a polyamide which may beheatsoftened at a convenient temperature. Thus,

these stiffeners may then be temporarily softened to conform with thelast, either by solvent or heat treatment, respectively. The polyamidesmay also be advantageously employed in the sole area of the shoe. Forexample, the outsole i0, the heel lift E, and innersole i2 may be madefrom films or sheets comprising polyamides. Fillers such as Il may beconveniently prepared from a felt of polyamide fibers. 'I'he heel 5 maybe built up of a series of layers comprising polyamide or, further, itmay be molded directly in one piece from a composition comprisingpolyamide. The present invention as embodied in Figure 2 involves theattachment of sole I0 to innersole i2 by means of stitching l5. It isunderstood that such stitching may also advantageously be prepared frompolyamide fibers. Wire or textile fabrics comprising polyamide mayalso'be used for the lacing 2|.

In addition to the sole illustrated in the drawing the present inventionis applicable to the other well known types of shoe construction, forexample, the Littleway, turn, stitchdown, nailed and cemented. Amongmany 'types of mens and womens footwear which may be fabricatedaccording to the present invention may be mentioned sport shoes,including golf, tennis, track,

' basketball, baseballl football, riding, bowling, hiking, hunting andskating shoes; work shoes, including safety shoes; boots; waterproof orwaterof weights, surface appearances, and physical properties.Sincethese may be supplied in uniform quality and at moderate cost, shoefabrication processes are at once broadened in scope and simplified inpractice. The appearance of leather footwear is `naturally determined bythe surface and structure of the animal hide employed, whereas the manyand varied operations which are applicable to the preparation andmodification of upper stock comprising polyamide open a vista of noveland attractive styles in footwear. Uniformity of supply and cost char-Examples of additional polyamides useful in the practice of thisinventioninclude materials such as polytetramethylene sebaCamide,polypentamethylene adipamide, polypentamethylene sebacamide,polyhexamethylene suberamide, polyhexamethylene sebacamide,polyoctamethylene adipamide, polydecamethylene carbamide,poly-p-xylylene sebacamide, polydecamethylene phenylenediacetamide, thepolyamide derived from 3,3'diaminodipropyl ether and adipic acid,polymerized B-aminocaproic acid, polymerized 9aminononanoic acid,andpolymerized 9, 10, or 12-aminostearic acid. Mixtures of preformedpolyamides may also b used. Particularly useful are the interpolyamideswhich are obtained by polymerization of a mixture of polyamide-formingreactance, e. g., a mixture of hexamethylenediamine, adipic acid and/orsebacic acid, caprolactam and/or 12-aminostearic acid. In the polyamidesof this invention the average number of carbon atoms separating theamide groups in the polymer chain is at least two. The term linearpolyamide as used herein includes not only polyamides andinterpolyamides obtained solely from polyamide-forming reactants butalso all linear polymers containing a. plurality of amide (includingthioamide) groups in the main chain of atoms, i. e., groups of thestructure A R Il ,-C-N- where A is oxygen or sulfur and Ris hydrogen ora monovalent hydrocarbon radical. These modified polyamides are obtainedby including with the polyamide-forming reactants other linearpolymer-forming reactants, such as amino alcohols and hydroxy acids. Asexamples of such modified polyamides may be mentioned the ester-amideinterpolymers, as for instance those derived from diamines, dibasicacids, and amino alcohols; those derived from diamines, dibasic acidsand hydroxy acids; those derived from dibasic acids and amino alcohols;and those derived from amino acids and hydroxy acids. Although theseproducts contain ester linkages, they may be referred to as polyamides,since they contain a plurality of amide linkages as an integral part ofthe main chain of atoms in the polymer, and retain many lof theAdesirable properties of the simple polyamides. Like the simplepolyamides, these modilied polyamides do not exhibit the fiber-formingproperties which give evidence of the toughness and potential durabilityrequired in this invention until their intrinsic viscosity is at least0.4. The term "polyamide also includes polycarbamates and their sulfuranalogs.

The articles`of footwear embodied in the present invention present manyadvantages to manufacturer and consumer-alike. The synthetic mateiialsdescribed herein as advantageously employed in the construction of thepresent invention may be had by the manufacturer in a variety acteristicof this polyamide upper stock provides for a more constant and reliableraw material source to the manufacturer and permits consideration ofnovel types of mass production equipment hitherto unusable by shoemanufacturers when only hides of natural leather varying in size,thickness, condition, and the like are available. In contrast to thepoor resistanceof previously tried leather substitutes to the repeatedflexing encountered in localized areas of the shoe upper, the upperstock comprising polyamide used in this invention exhibits excellentdurability in this respect. VFor example, a shoe made as described inExample I has been` given normal usage for a period of five months andthe upper shows'no evidence of cracking or failure of any kind Whileanother shoe containing a good grade of a commercial artificial leatheras upper material and given identical wear, is marred by extensivecracking of the upper. Furthermore, the footwear of this invention farexceeds footwear containing upper material of natural leather withregard to scuif resistancewhen subjected to hard usage. For example, ashoe made as described in Example II, but in the design of Fig. 2 andwith a cemented construction, has .been given rough usage for a periodof two months and the upper shows no evidence of surface marring orwrinkling while a shoe similarly prepared but containing a leather upperand given identical usage has been rendered unsightly due to seriousmarring of the upper by cuts and scratches as well as by extensivewrinkling.

A shoe in which the upper comprises a coated knit fabric of the kinddescribed in Example VI is a particularly valuable form of thisinvention because of the great extensibility of this upper stock andbecause of its freedom from the appearance of a fabric pattern. Thesepolyamide coated knitted fabrics have an unusual resistance to crackingunder the severe conditions of ilexing which are encountered inlocalized areas of the shoe upper.

The quality of extensibility is advantageous in the ease with which thisupper stock is fabricated into shoes, especially the pulling over stepin the lasting operation, in which these preferred compositions comparevery favorably with natural leather in their workability. In contrastthe artificial leathersy heretofore known have been notably lacking inextensibility regardless of the nature of either the coating or backingused.

In connection with the hereinabove-mentioned extensibility of` the uppermaterials of the invention, it may be Observed that the application tothem @fit-he conventional lasting operations results in -at least a 20%averageincrease in area, thesaid increase being brought about by acombination of longitudinal and transverse stretching, in the portion ofthe upper materials directly affected; which increase in area isleffected without the development of clothiness.

The above mentioned complete freedom from the appearance of a fabricpattern which is made possible by the polyamide coated knitted fabri isan important feature in the manufacture o shoes from artificial leathermaterials. This appearance of a fabric pattern. which is designatedclothiness, often appears in shoes made from coated fabrics in thoseportions .(e. g., the toe) which have been subjected vto a severestretching in the lasting operation. Thus, many and soapy water.` whilewhite leather shoes rapidly becomev gray with wear and must berepeatedly whitened with finishing agents. Conventional shoe polishesauch as wax postes or emulsions are effectively employed on the articlesof this invention in producing the high luster desired in many footwearapplications.

As many apparently widely different embodiments of this invention may bemade without departing from the spirit and scope thereof, it is to beunderstood that I do not limit myself to the specific'` embodimentsthereof except as defined in the appended claims.

I claim:

1. As an integral part of a shoe, a polyamide coated fabric in unitarystretched condition incident to forming said shoe, the coating on saidfabric being not greater than 0.03 inch in ave erage total thickness andin said stretched con-d dition substantiallv completely concealing thefabric pattern of said fabric, said polyamide being that obtainable froma polymer-forming composition comprising hexamethylenediamine, adipicacid. and caprolactam.

2. In a process for producing shoes, the steps which comprise coating astretchable textile fabric with a synthetic linear polyamide in asolvent therefor, omitting evaporative removal of a substantial amountof solvent during the production of said coating, -then subjecting thesame to heat and pressure wherein a high degree of porosity is impartedto the coating on said fabric without injury to the filaments thereof,and subjecting the polyamide coated fabric to unitary stretching inincorporating said coated fabric into a shoe.

3. As an integral part of a shoe, a polyamide coated fabric in unitarystretched condition incident to forming said shoe, the coating on saidfabric being not greater than 0.03 inch in average total thickness andin said stretched condition substantially completely concealing thefabric pattern of said fabric, said polyamide being that obtainable froma polymer-forming composition comprising hexamethylenediamine, adipicacid. sebacic acid, and caprolactam. PAUL R. AUSTIN.

